CompTIA Cert Guide

ContentsChapter 10Chapter 11Permissions and Ownership 289“Do I Know This Already?” Quiz 289Working with Permissions 292Permission Trio Bits 292Manipulating Permissions 294Numeric Mode 294Symbolic Mode 296Special File Permissions 297Special Bit Permissions 298Setting the SUID Bit on Files 299Setting the SGID Bit on Files 300Setting the SGID Bit on Directories 301Setting the Sticky Bit 302Finding Files by Permission 302Default Permissions 303Changing User Ownership 305Changing Group Ownership 306Summary 307Exam Preparation Tasks 307Review All Key Topics 307Define Key Terms 308Review Questions 308Customizing Shell Environments 311“Do I Know This Already?” Quiz 311Working Within the Shell 314Environment Variables 315Variable Scope 316Setting Variables from a Child 316Setting and Unsetting Variables 317Subshells 318The env Wrapper 319Extending the Shell 320Global and User Settings 320A Login Shell Session 321A Non-Login Shell Session 321The PATH 322Aliases and Functions 323Functions 323PS1 324Adding More Dynamic Content 325PS2 326Creating New Users (skeleton) 326xi

xiiCompTIA Linux / LPIC-1 Cert GuideChapter 12Localization and Internationalization 327Time Zones 327Displaying Time 328Setting Time Zones 328Character Encoding 329Representing Locales 330Fallback Locales 331Contents of a Locale 331How Linux Uses the Locale 332Converting Files Between Encodings 334Exam Preparation Tasks 334Review All Key Topics 334Define Key Terms 335Review Questions 335Shell Scripting 339“Do I Know This Already?” Quiz 339Basics of Scripting 342Running a Script 343Good Design 343Managing Your Scripts 344Shell Script Commands 344Use the Output of Another Command 344Do Math 345Conditions 346Testing Files 348An Easier Test Syntax 348Testing Strings 349Testing Integers 350Combining Multiple Tests 351Case Statements 351Loops 353For Loops 353Sequences 354While Loops 355Reading from stdin in a Loop 356Interacting with Other Programs 356Returning an Error Code 357Accepting Arguments 357Transferring Control to Another Program 358Exam Preparation Tasks 359Review All Key Topics 359Define Key Terms 360Review Questions 360

ContentsChapter 13Chapter 14Basic SQL Management 365“Do I Know This Already?” Quiz 365Database Basics 368Types of Databases 368Key-Value Databases 368Relational Databases 369Schemaless Databases 370Learning SQL 371Using SQLite 371SQL Basics 372Keywords Versus Data 372Selecting Data 373Being Choosy 374Multiple Conditions 376Sorting 377Limiting Results 378Working with Multiple Tables 378Writing Queries with Joins 379Cleaning Up the Query 381Advanced Joins 381Left Versus Right Joins 384Null 384Subselects 385Grouping Data 386Inserting Data 387Updating Data 388Deleting Data 388Creating Tables 388Summary 390Exam Preparation Tasks 390Review All Key Topics 390Define Key Terms 391Review Questions 392Configuring User Interfaces and Desktops 397“Do I Know This Already?” Quiz 397Quick Overview of X 400How X Works 400Window Managers 401Linux Desktops 402The Xorg System 402The Xorg Configuration File 402Fonts in X 405Tuning X 406xiii

xivCompTIA Linux / LPIC-1 Cert GuideChapter 15X Display Managers 408Into and Out of X 409Accessibility Options 410Sticky/Repeat Keys 410Slow/Bounce/Toggle Keys 411Mouse Keys 411High Contrast/Large Print Desktop Themes 412Screen Reader 412Braille Display 413Screen Magnifier 413Onscreen Keyboard 413Remote Clients 413Summary 415Exam Preparation Tasks 415Review All Key Topics 415Define Key Terms 415Review Questions 416Managing Users and Groups 419“Do I Know This Already?” Quiz 419User Account Fundamentals 422What Accounts Are What? 422Normal User Accounts 423User Entries in /etc/passwd 423Special Login Files 424Group Accounts 425Group Entries in /etc/group 427Group Passwords 427Adding Users and Groups 428Adding Users with useradd 428The useradd Defaults 429Adding Groups with groupadd 431Modifying Users and Groups 431Modifying User Accounts with usermod 431Modifying Groups with groupmod 432Removing Users and Groups 433Removing Users 433Removing Groups 434The Shadow Suite 435Encrypted Passwords and Shadow Fields 435shadow File Permissions 437Changing Accounts 437Aging Passwords 438User Variables 440

ContentsChapter 16Chapter 17Summary 440Exam Preparation Tasks 441Review All Key Topics 441Define Key Terms 442Review Questions 442Schedule and Automate Tasks 445“Do I Know This Already?” Quiz 445The Cron System 447Configuring crontabs 447Using the crontab Command 447Matching Times 448Spelling Out Month and Day Names 449Making Multiple Matches 449Step Values 450Putting the crontab Together 450Issues About Path 450Dealing with Output 451Nicknames 452Other Files 452System crontabs 453Convenience crontabs 454Restricting Access 454Anacron 455Running Ad-hoc Jobs 456The at Command 456The batch Command 458Summary 459Exam Preparation Tasks 460Review All Key Topics 460Define Key Terms 460Review Questions 461Configuring Print and Email Services 465“Do I Know This Already?” Quiz 465Managing Printers and Printing 467The Print Spooler 467Network Printing Protocols 467The CUPS Daemon 468The CUPS Pipeline 468Configuring CUPS 470CUPS Maintenance 474Printer State 475Maintenance and Administration Pull-downs 476xv

xviCompTIA Linux / LPIC-1 Cert GuideChapter 18Administration Menu 476Jobs List 477Command Line Tools 477Legacy Tools 477lp/lpr 478lpstat 478lpq 479lprm 479CUPS Tools 480cupsaccept/cupsreject 480cupsenable/cupsdisable 481cupsctl 481Configuration Files 482Troubleshooting Printing 482Try Printing from the Command Line 482Was the Job Queued? 483Can CUPS Send the Job to the Printer? 483Turn On Debugging 483Mail Transfer Agent Basics 484How Email Flows 484Mail User Agent 484Mail Transfer Agent 485The Language of Email 485Linux MTAs 486Domain Name System 487Mail Delivery Agent 488Mail Server 488Creating Aliases and Forwarding Email 489Committing Changes 489Other Types of Aliases 490User-Defined Forwarding 491Managing Queues 491Summary 492Exam Preparation Tasks 492Review All Key Topics 492Define Key Terms 493Review Questions 493Logging and Time Services 497“Do I Know This Already?” Quiz 497Maintain System Time 500Not One, But Two Clocks 500Working with the System Clock 500Working with the Hardware Clock 503

ContentsChapter 19The hwclock Command 503Synchronizing Time Between Clocks 504Network Time Protocol 504Setting the Time from the Command Line 505The pool.ntp.org Servers 505Configuring ntpd 506Monitoring ntpd 507System Logging 508systemd and syslog 508syslog 509The logger Command 512Configuring syslogd 512Other syslog Implementations 514systemd Logging 514Querying the Log 515Configuring journald 519Rotating Logs 520Configuring Log Rotation 520Dealing with Open Files 522Summary 522Exam Preparation Tasks 523Review All Key Topics 523Define Key Terms 524Review Questions 524Networking Fundamentals 529“Do I Know This Already?” Quiz 529Conceptual Overview of Networking 532Necessary Configuration Information 533IP Addresses 533Networks and Hosts 534Address Class Ranges 534Using the Bits to Determine Class 535Network Masks 536Using Default Network Masks 536Gateway Addresses, or “Do I Dial with the Area Code?” 537Broadcast Addresses 538Custom Network Masks 538Determining a Custom Network Mask 538Additional Protocols 541Common Ports 542IPv6 544xvii

xviiiCompTIA Linux / LPIC-1 Cert GuideChapter 20Managing Interfaces 545Viewing IP Information 545Red Hat Interface Configuration 547Debian Interface Configuration 548Viewing and Configuring Gateway Addresses 550Viewing the Default Gateway 550Configuring a Default Gateway 550Local Name Configuration 551Network Configuration Utilities 553Network Utility Examples 554The ifconfig Command 555The route Command 555DHCP Client Tools 556The host, getent, and dig Commands 557Hostname Utilities 559Using netstat 559The ping Command 562Using traceroute 563Using tcpdump 565Summary 566Exam Preparation Tasks 566Review All Key Topics 566Define Key Terms 567Review Questions 567System Security 571“Do I Know This Already?” Quiz 571Gaining Access to the root Account 574The su Command 574The sudo Command 575Providing Services on Demand 576Using inetd and xinetd 576inetd Configuration Files 577xinetd Configuration Files 578Using TCP Wrappers for Securing Services 581inetd and TCP Wrappers 581xinetd and TCP Wrappers 582The hosts.allow and hosts.deny Files 582Wrapper Read Order 583Format of hosts.allow and hosts.deny 583Sample Configurations 583Using Rule Options 585

ContentsUnderstanding Permission Problems 586Finding Files by Permissions 587GnuPG Keys 587Secure Shell 590SSH Components 591Using SSH Client Utilities 592Additional Security Features 596Summary 597Exam Preparation Tasks 598Review All Key Topics 598Define Key Terms 599Review Questions 599Chapter 21 Final Preparation 603How to Prepare for the LPI Exams 604Caveat and Warning 604Exam Objectives 604Important Exam Facts 605Right Before Your Exam Starts 605How to Look at the Objectives 606Studying for the Exams—What to Do 608Machines or Virtual Machines? 609Studying for the Exams—What Not to Do 609Don’t Believe Everything 610Don’t Worry, Be Happy 610LPI Certifications and Distributions 610You Have to Install Something 611LPI Exam Question Types 611Single Answer Multiple Choice 612Choose Two/Choose Three 613Choose All That Apply 613Fill in the Blank 615Final Recommendations 616Summary 617Appendix A Answers to the “Do I Know This Already?” Quizzes and ReviewQuestions 619Glossary 659Index 693xix

xxCompTIA Linux / LPIC-1 Cert GuideAbout the AuthorsRoss Brunson has more than 20 years of experience as a Linux and Open Sourcetrainer, training manager, and technologist and is author of the popular LPIC-1Exam Cram (QUE Publishing).Ross is currently senior training/certification engineer at SUSE and recently spentalmost five years as the director of member services for the Linux Professional Institute, where he contributed to placing several LPI courses into the Cisco Networking Academy, conducted dozens of Train-the-Trainer sessions, and provided salesenablement support for the worldwide Master Affiliate network spanning more than100 countries.Ross holds a number of key IT certifications and is also author of several successfultechnical books and dozens of technical courses for major organizations (includingthe first LPI Certification Bootcamps). He is skilled at both contributing to andbuilding community around IT products.He lives in Paradise Valley, Montana, with his family and enjoys traveling far andwide, winter sports, and photography.Sean Walberg has more than 20 years of experience as a Linux administrator, network engineer, and software developer. He has written extensively on Linux certification for IBM and NetDevGroup, and has contributed to other books both as anauthor and technical reviewer.Sean currently works at Northfield IT and is responsible for infrastructure automation for a large professional sports league. Using tools like Ruby, shell scripts, andChef, he automates the creation and maintenance of more than a thousand servers and the associated network infrastructure. Sean works closely with developersto scale applications to the demands of an internationally recognized series of webproperties.He lives in Northern Virginia with his wife and three sons.

DedicationsAbout the Contributing AuthorAt the impressionable age of 14, William “Bo” Rothwell crossed paths with aTRS-80 Micro Computer System (affectionately known as a “Trash 80”). Soonafter the adults responsible for Bo made the mistake of leaving him alone with theTRS-80. He immediately dismantled it and held his first computer class, showinghis friends what made this “computer thing” work.Since this experience, Bo’s passion for understanding how computers work andsharing this knowledge with others has resulted in a rewarding career in IT training.His experience includes Linux, Unix, and programming languages such as Perl,Python, Tcl, and BASH. He is the founder and president of One Course Source,an IT training organization.About the Technical ReviewerTed Jordan has more than 25 years of programming, administration, and trainingexperience in UNIX, IRIX, Solaris, and Linux. His career spans from GeneralMotors, Silicon Graphics, to SUN. He holds the LPIC, Linux , and SUSE Linuxcertifications. He is the founder and president of two successful startups, the latestbeing Funutation Tech Camps where he teaches kids to code computer games.Ted lives with his family near Worcester, Massachusetts, and enjoys tennis, golf,and karaoke.DedicationsRoss Brunson: To my good friends, Andres and Ken, we few, we happy few. With love andrespect to my wife and daughter, for putting up with my being locked in my office writing andediting while the sun shone and breezes blew. To every student/attendee/customer I’ve ever taughta Linux topic to, it’s really all for you.Sean Walberg: To my amazingly beautiful and intelligent wife, Rebecca. The completion of thisbook happens to coincide with the start of our new adventure together, and I can think of no oneelse I’d like to share it with.xxi

xxiiCompTIA Linux / LPIC-1 Cert GuideAcknowledgmentsRoss Brunson: To the ultimate nerd-herders, Ellie Bru and Mary Beth Ray;Ellie for her ability to take the peeping and muttering of technical geeks and makeit something useful, workable, and often profound, and Mary Beth for believing inauthors and technologists, even when we break her heart by blowing out deadlinesand not doing what we say we will on time.To my little brother, Leighton, who will make the most awesome history professorone day.To Sean Walberg, who I have known and respected over several book projects,years of interactions in the LPI community, and all the way back to the Cramsessiondays with Qcumber and the gang.To Bo Rothwell and Ted Jordan, awesome technical editors and great guys, as wellas two of the best technical trainers it is my pleasure to know.Sean Walberg: To the crew at Pearson, most notably Geneil, Ellie, and Mary Beth:This project is better because of your patience and input.The technical editors, Ted and Bo, also deserve special mention. Not only did youfix my technical missteps, but your years of experience as trainers pointed out whereI was using some words that were going to confuse new Linux users.Finally, my knowledge of Linux wasn’t earned alone. It came through long nights,hard work, and lots of arguing with people like Marc Caron, Hany Fahim, PatrickleMaistre, Daniel Little, Dave Rose, and of course, my co-author Ross Brunson whoI’m happy to have known for more than 15 years.

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xxivCompTIA Linux / LPIC-1 Cert GuideIntroductionThis book was written to help people learn to use Linux. Not just learning Linux bymemorizing commands, but learning Linux by understanding how the parts are puttogether. Approaching Linux from this perspective means that you’ll know where tolook when you run up against something new and are better suited to handle problems as they come up. The authors of this book are experienced writers, but moreimportantly, are in the trenches every day.The CompTIA Linux exams LX0-103 and LX0-104 and Linux Professional Institute LPIC Level 1 exams 101-400 and 102-400 (which are identical) encompass theknowledge necessary to become an entry level Linux administrator. There are certainly other books that cover this material, but this is the one that looks beyond theexam to preparing people for the Linux workforce.You don’t need to be taking either the Linux or LPIC exams to get use out of thisbook. Concepts such as filesystems, hardware, shell usage, and managing email systems are needed in the workforce, and we, as authors, have endeavored to produce abook that is just as helpful to all new Linux users.Goals and MethodsThe goal of this book is to provide a guided tour of the Linux operating systemwith an eye to achieving an entry-level certification at the completion of the book.Readers with no intention of writing an exam will still find this book helpful as thecertification content, by design, closely maps to the skills required by a Linux administrator. The authors also hope that the examples and practical advice in this textprove valuable well after the reader is done with the book.The Linux and LPIC Level 1 certification exams are broken into specific topicsthat build upon each other, and the book does its best to mirror those. Not onlydoes this provide a natural progression to learning Linux, but for those who are taking the exam, allows them to focus on troublesome areas.Linux commands and their output are interspersed with the text to provide concreteexamples right next to the description. Examples, for the most part, are adaptationsof real world usage rather than being contrived. And since no good Linux graybeardshould take himself too seriously, the authors have done their best to inject somelevity into the discussion.

IntroductionWho Should Read This Book?This book was written for people who want to learn Linux—people just getting intothe information technical field, Windows administrators who want to branch outto Linux, or students looking to understand Linux. Even if you’re not taking theLinux or LPIC Level 1 exams you’ll find this book helpful.The first half of the book focuses on concepts and basic command usage, while thesecond half turns the attention to applications found in a

vi CompTIA Linux / LPIC-1 Cert Guide Querying Packages 77 Package Management with YUM 80 Installing Packages 80 Fetching Updates 83 Finding Packages to Install 83 Configuring Yum 84 Summary 86 Exam Preparation Tasks 86 Review All Key Topics 86 Define Key Terms 87 Review Questions 88 Chapter 4 Basic Command Line Usage 91